From mboxrd@z Thu Jan 1 00:00:00 1970 From: Daniel Vetter Subject: Re: [PATCH 2/2] drm/i915: wait for IPS_ENABLE when enabling IPS Date: Fri, 20 Sep 2013 10:12:32 +0200 Message-ID: <20130920081232.GI32145@phenom.ffwll.local> References: <1379620986-1702-1-git-send-email-przanoni@gmail.com> <1379620986-1702-3-git-send-email-przanoni@gmail.com> <20130919202433.GC7745@nuc-i3427.alporthouse.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from mail-ea0-f180.google.com (mail-ea0-f180.google.com [209.85.215.180]) by gabe.freedesktop.org (Postfix) with ESMTP id D25F0E5C3B for ; Fri, 20 Sep 2013 01:12:17 -0700 (PDT) Received: by mail-ea0-f180.google.com with SMTP id h10so64226eaj.25 for ; Fri, 20 Sep 2013 01:12:16 -0700 (PDT) Content-Disposition: inline In-Reply-To: <20130919202433.GC7745@nuc-i3427.alporthouse.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: intel-gfx-bounces+gcfxdi-intel-gfx=m.gmane.org@lists.freedesktop.org Errors-To: intel-gfx-bounces+gcfxdi-intel-gfx=m.gmane.org@lists.freedesktop.org To: Chris Wilson , Paulo Zanoni , intel-gfx@lists.freedesktop.org, Paulo Zanoni List-Id: intel-gfx@lists.freedesktop.org On Thu, Sep 19, 2013 at 09:24:33PM +0100, Chris Wilson wrote: > On Thu, Sep 19, 2013 at 05:03:06PM -0300, Paulo Zanoni wrote: > > From: Paulo Zanoni > > > > At the end of haswell_crtc_enable we have an intel_wait_for_vblank > > with a big comment, and the message suggests it's a workaround for > > something we don't really understand. So I removed that wait and > > started getting HW state readout error messages saying that the IPS > > state is not what we expected. > > > > I investigated and concluded that after you write IPS_ENABLE to > > IPS_CTL, the bit will only actually become 1 on the next vblank. So > > add code to wait for the IPS_ENABLE bit. We don't really need this > > wait right now due to the wait I already mentioned, but at least this > > one has a reason to be there, while the other one is just to > > workaround some problem: we may remove it in the future. > > > > The wait also acts as a POSTING_READ which we missed. > > > > Signed-off-by: Paulo Zanoni > > Both patches: > Reviewed-by: Chris Wilson > > I was thinking that maybe the intel_wait_for_vblank would be better from > a documenting perspective - and it would also give warnings for trying > to enable ips whilst the pipe was off. But you would still need the wait > for IPS_ENABLE as confirmation anyway. Both queued for -next, thanks for the patches&review. -Daniel -- Daniel Vetter Software Engineer, Intel Corporation +41 (0) 79 365 57 48 - http://blog.ffwll.ch